1. Field of the Invention
The present invention relates to an RFID (Radio Frequency IDentification) reading method capable of detecting, without omission, the presence of the RFIDs provided to goods conveyed by a conveying apparatus. Moreover, the present invention relates to an RFID reading system and a control apparatus for carrying out such an RFID reading method, and a computer program product for such control apparatus.
2. Description of Related Art
In recent years, RFID media such as noncontact type IC tags to and from which information is writable and readable in a noncontact manner have sprung into wide use. For example, by conveying a goods or the like in a state of being provided with a noncontact type RFID medium, it is enabled to read the information recorded on the noncontact type RFID medium by a reader/writer provided exterior and inspect the goods or the like based on the read information.
However, when the reader/writer reads the information from the noncontact type RFID medium, it is necessary that the noncontact type RFID medium and the reader/writer are present within a predetermined distance for a predetermined time or longer. In particular, in a case where the goods or the like provided with the noncontact type RFID medium is being moved by a conveying apparatus such as a conveyor, whether the presence of the noncontact type RFID medium can be detected with reliability or not is an important technical problem.
Conventionally, in order that the presence of the noncontact type RFID medium can be reliably detected even when the goods or the like provided with the noncontact type RFID medium is being moved by a conveying apparatus such as a conveyor, the conveyance speed of the conveyor or the like is reduced at the time of the detection. For example, by reducing the conveyance speed of a forklift which is normally 133 meters per minute, to 30 meters per minute at the time of the inspection, the time for reading the information stored in the noncontact type RFID medium by the reader/writer is secured. This results in a reduction of the overall conveyance efficiency because the inspection speed becomes a bottleneck.
To solve such a problem, for example, Japanese Patent Application Laid-Open No. 2004-094556 discloses an inspecting apparatus capable of, only when the presence of the noncontact type RFID medium cannot be detected by a normal detection gate where the reader/writer is placed, detecting the presence of the noncontact type RFID medium again by another reader/writer by leading the goods or the like to a different path. According to this prior art, the presence of the noncontact type RFID medium can be more reliably detected without any reduction in the conveyance speed of the goods or the like.
Moreover, Japanese Patent Application Laid-Open No. 2004-085400 discloses an IC product inspecting apparatus in which the reader/writer moves in synchronism with the speed at which the IC product provided with the noncontact type RFID medium is conveyed. According to this prior art, information can be read without any reduction in the conveyance speed of the goods or the like with similar accuracy to when the information stored in the noncontact type RFID medium is read with the reader/writer being stopped.